Hibernate 驗證器 · ZetCode 中文系列教程

# Hibernate 驗證器原文：http://zetcode.com/java/hibernatevalidator/ 在本教程中，我們展示了如何使用 Hibernate 驗證器來驗證數據。驗證從用戶那里收到的輸入以保持數據完整性是應用邏輯的重要組成部分。驗證被合并到 Java Web 框架中，例如 Stripes，Ninja 框架或 Play 框架。 ## Bean 驗證 Bean 驗證是 Java EE 6 平臺中引入的驗證模型。約束通過以 JavaBeans 組件的字段，方法或類上的注解形式的約束來支持 Bean 驗證模型。也可以使用 XML 驗證描述符。 ## Hibernate 驗證器定義 Hibernate 驗證器是 Bean 驗證的參考實現。 Hibernate Validator 允許表達和驗證應用約束。默認的元數據源是注解，可以通過使用 XML 進行覆蓋和擴展。它不依賴于特定的應用層或編程模型，并且可用于服務器和客戶端應用編程。 ## Hibernate 驗證器命令行應用在下面的示例中，我們在一個簡單的命令行應用中使用了 Hibernate Validator。 `pom.xml` ```java <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>HibernateValidation</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> </properties> <dependencies> <dependency> <groupId>javax.el</groupId> <artifactId>javax.el-api</artifactId> <version>2.2.4</version> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>javax.el</artifactId> <version>2.2.4</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator-cdi</artifactId> <version>5.2.4.Final</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.16.8</version> <scope>provided</scope> </dependency> </dependencies> </project> ``` Maven `pom.xml`包含 Hibernate Validator 和 Lombok 庫的依賴項。龍目島用于減少一些樣板。 `Car.java` ```java package com.zetcode.bean; import javax.validation.constraints.Max; import javax.validation.constraints.Min; import javax.validation.constraints.NotNull; import javax.validation.constraints.Size; import lombok.Data; @Data public class Car { private Long Id; @NotNull @Size(min=4, max=50) private String name; @Min(value = 1000) @Max(value = 5000000, message="There is no such expensive car") private int price; public Car() {} public Car(String name, int price) { this.name = name; this.price = price; } } ``` 我們有一個`Car` bean，我們在其中驗證數據。 ```java @Data public class Car { ``` `Car` bean 用 lombok 的`@Data`注解修飾。它會自動創建獲取器和設置器方法，`equals()`方法，`toString()`方法和`hashCode()`方法。 ```java @NotNull @Size(min=4, max=50) private String name; ``` `@NotNull`注解指出`name`屬性可能不是`null`。 `@Size`注解設置屬性的最小和最大大小。 ```java @Min(value = 1000) @Max(value = 5000000, message="There is no such expensive car") private int price; ``` `@Min`約束設置`price`屬性的最小值。 `message`元素用于創建錯誤消息。 `ClientApp.java` ```java package com.zetcode.client; import com.zetcode.bean.Car; import java.util.Set; import javax.validation.ConstraintViolation; import javax.validation.Validation; import javax.validation.Validator; import javax.validation.ValidatorFactory; public class ClientApp { private static Validator validator; public static void main(String[] args) { Car car1 = new Car("Volvo", 29000); Car car2 = new Car("Skoda", 900); Car car3 = new Car(null, 29000); Car car4 = new Car("Cit", 21000); Car car5 = new Car("Bentley", 8000000); ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); validator = factory.getValidator(); validate(car1); validate(car2); validate(car3); validate(car4); validate(car5); } public static void validate(Car car) { Set<ConstraintViolation<Car>> cvs = validator.validate(car); for (ConstraintViolation<Car> cv : cvs) { System.out.println(cv.getPropertyPath() + ": " + cv.getMessage()); } } } ``` 在客戶端應用中，我們創建五個汽車對象并對其進行驗證。 ```java Car car1 = new Car("Volvo", 29000); Car car2 = new Car("Skoda", 900); Car car3 = new Car(null, 29000); Car car4 = new Car("Cit", 21000); Car car5 = new Car("Bentley", 8000000); ``` 將創建五個汽車對象。四輛車的值未通過驗證過程。例如，斯柯達汽車的價格太低；即低于最小值 1000。 ```java ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); validator = factory.getValidator(); ``` 驗證工廠與`buildDefaultValidatorFactory()`方法一起使用。在工廠，我們使用`getValidator()`方法獲得了驗證器。建議緩存驗證器工廠，因為創建起來很昂貴。 ```java Set<ConstraintViolation<Car>> cvs = validator.validate(car); ``` 使用驗證程序的`validate()`方法驗證汽車。 ```java for (ConstraintViolation<Car> cv : cvs) { System.out.println(cv.getPropertyPath() + ": " + cv.getMessage()); } ``` 我們將打印錯誤消息以了解違反約束的情況。 ```java price: must be greater than or equal to 1000 name: may not be null name: size must be between 4 and 50 price: There is no such expensive car ``` 運行應用時，我們會收到這些錯誤消息。 ## Hibernate 驗證器 Web 應用在第二個示例中，我們在 Web 應用中利用了 Hibernate Validator。該應用部署在 Apache Tomcat 服務器上。該應用的來源可從作者的 [Github 倉庫](https://github.com/janbodnar/HibernateValidator)中獲得。 ![Project structure](https://img.kancloud.cn/3d/cc/3dcc447937c9c0c7613beee62c72008c_237x401.jpg) 圖：項目結構該圖顯示了 NetBeans 中的項目結構。 `context.xml` ```java <?xml version="1.0" encoding="UTF-8"?> <Context path="/HibernateValidation"/> ``` `context.xml`文件包含應用的上下文路徑。 `pom.xml` ```java <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>HibernateValidation2</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <name>HibernateValidation2</name> <dependencies> <dependency> <groupId>javax</groupId> <artifactId>javaee-web-api</artifactId> <version>7.0</version> <scope>provided</scope> </dependency> <dependency> <groupId>jstl</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> <dependency> <groupId>javax.el</groupId> <artifactId>javax.el-api</artifactId> <version>2.2.4</version> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>javax.el</artifactId> <version>2.2.4</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator-cdi</artifactId> <version>5.2.4.Final</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.16.8</version> <scope>provided</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.1</version> <configuration> <source>1.8</source> <target>1.8</target> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>2.3</version> <configuration> <failOnMissingWebXml>false</failOnMissingWebXml> </configuration> </plugin> </plugins> </build> </project> ``` Maven `pom.xml`包含 Java EE Web API，Hibernate Validator 和 Lombok 庫的依賴項。 `index.jsp` ```java <%@page contentType="text/html" pageEncoding="UTF-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Validation</title> </head> <body> <p> Enter your name and email: </p> <form method="post" action="Greet"> Name: <input type="text" name="username"> <br> Email: <input type="text" name="email"> <br> <input type="submit" value="Submit"> </form> </body> </html> ``` `index.jsp`是我們應用的入口。它包含一個帶有兩個字段的 HTML 表單：用戶名和電子郵件。在這些字段中輸入的值將由應用驗證。 ```java <form method="post" action="Greet"> ... </form> ``` 提交表單后，將調用`Greet` Servlet。 `hello.jsp` ```java <%@page contentType="text/html" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Greeting</title> </head> <body> Hello <c:out value="${param.username}"/>! <br> Your email is <c:out value="${param.email}"/>. </body> </html> ``` 當輸入數據通過驗證測試時，將顯示`hello.jsp`頁面。顯示輸入的數據。 `valError.jsp` ```java <%@page contentType="text/html" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Error</title> </head> <body> <p> <c:forEach var="err" items="${errMsg}"> <c:out value="${err}"/> <br> </c:forEach> </p> </body> </html> ``` 如果驗證失敗，則顯示`valError.jsp`。它顯示了存儲在`errMsg`屬性中的錯誤消息。該屬性是在驗證過程中設置的。 `User.java` ```java package com.zetcode.bean; import javax.validation.constraints.Pattern; import lombok.Data; import org.hibernate.validator.constraints.NotEmpty; @Data public class User { @NotEmpty private String name; @NotEmpty @Pattern(regexp="^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\\.[a-zA-Z.]{2,5}", message="Please provide a valid email address") private String email; } ``` `User` bean 用 Lombok 和 Hibernate Validator 注解修飾。 ```java @NotEmpty private String name; ``` `@NotEmpty`注解導致用戶名不能為空。 ```java @NotEmpty @Pattern(regexp="^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\\.[a-zA-Z.]{2,5}", message="Please provide a valid email address") private String email; ``` 電子郵件不能為空，并且必須匹配給定的模式。用`@Pattern`注解設置模式。 `DoValidate.java` ```java package com.zetcode.util; import com.zetcode.bean.User; import java.util.ArrayList; import java.util.List; import java.util.Set; import javax.validation.ConstraintViolation; import javax.validation.Validation; import javax.validation.Validator; import javax.validation.ValidatorFactory; public class DoValidate { public static List<String> validate(User user) { List<String> errors = new ArrayList(); ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); Validator validator = factory.getValidator(); Set<ConstraintViolation<User>> cvs = validator.validate(user); if (!cvs.isEmpty()) { for (ConstraintViolation<User> cv : cvs) { StringBuilder err = new StringBuilder(); err.append(cv.getPropertyPath()); err.append(" "); err.append(cv.getMessage()); errors.add(err.toString()); } } return errors; } } ``` 驗證在`DoValidate`工具類中執行。 ```java if (!cvs.isEmpty()) { for (ConstraintViolation<User> cv : cvs) { StringBuilder err = new StringBuilder(); err.append(cv.getPropertyPath()); err.append(" "); err.append(cv.getMessage()); errors.add(err.toString()); } } ``` 當違反約束時，我們將創建錯誤消息列表。 `getMessage()`方法獲取約束沖突的錯誤消息。 ```java return errors; ``` 錯誤消息列表將返回給調用方。如果未檢測到違規，則該列表為空。 `Greeting.java` ```java package com.zetcode.web; import com.zetcode.bean.User; import com.zetcode.util.DoValidate; import java.io.IOException; import java.util.List; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet(name = "Greeting", urlPatterns = {"/Greet"}) public class Greeting extends HttpServlet { @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); String page = "/hello.jsp"; String username = request.getParameter("username"); String email = request.getParameter("email"); User user = new User(); user.setName(username); user.setEmail(email); List<String> errors = DoValidate.validate(user); if (!errors.isEmpty()) { request.setAttribute("errMsg", errors); page = "/valError.jsp"; } else { request.setAttribute("user", user); } RequestDispatcher disp = getServletContext().getRequestDispatcher(page); disp.forward(request, response); } } ``` `Greeting` Servlet 檢索請求數據并調用`DoValidate.validate()`工具方法。取決于驗證的結果，該 servlet 調度到`hello.jsp`或`valError.jsp`頁面。 ![Error message](https://img.kancloud.cn/92/b7/92b71142e3d500246adae698291960ae_591x346.jpg) 圖：錯誤消息如果電子郵件格式不正確，則應用將以錯誤消息響應。這是驗證過濾器教程。我們使用 Hibernate Validator，JSTL，JSP，Apache Tomcat 和 Maven 構建了一個控制臺和一個 Web 應用。您可能還需要查看一些相關的教程： [Java 驗證過濾器教程](/java/validationfilter/)， [Java 教程](/lang/java/)或 [Stripes 教程](/java/stripes/)。